1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * bpf-script-test-prologue.c
4 * Test BPF prologue
5 */
6 #ifndef LINUX_VERSION_CODE
7 # error Need LINUX_VERSION_CODE
8 # error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
9 #endif
10 #define SEC(NAME) __attribute__((section(NAME), used))
11
12 #include <uapi/linux/fs.h>
13
14 /*
15 * If CONFIG_PROFILE_ALL_BRANCHES is selected,
16 * 'if' is redefined after include kernel header.
17 * Recover 'if' for BPF object code.
18 */
19 #ifdef if
20 # undef if
21 #endif
22
23 #define FMODE_READ 0x1
24 #define FMODE_WRITE 0x2
25
26 static void (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) =
27 (void *) 6;
28
29 SEC("func=null_lseek file->f_mode offset orig")
30 int bpf_func__null_lseek(void *ctx, int err, unsigned long _f_mode,
31 unsigned long offset, unsigned long orig)
32 {
33 fmode_t f_mode = (fmode_t)_f_mode;
34
35 if (err)
36 return 0;
37 if (f_mode & FMODE_WRITE)
38 return 0;
39 if (offset & 1)
40 return 0;
41 if (orig == SEEK_CUR)
42 return 0;
43 return 1;
44 }
45
46 char _license[] SEC("license") = "GPL";
47 int _version SEC("version") = LINUX_VERSION_CODE;
48
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